Use protocol constants for ACK airtime window sizing

2026-02-04 14:40:34 +01:00
parent 373667ab8a
commit c3e5ba3a53
2 changed files with 11 additions and 3 deletions
--- a/include/lora_transport.h
+++ b/include/lora_transport.h
@@ -5,6 +5,14 @@
 #include "data_model.h"

 constexpr size_t LORA_MAX_PAYLOAD = 230;
+constexpr size_t LORA_FRAME_HEADER_LEN = 3; // msg_kind + dev_id_short
+constexpr size_t LORA_FRAME_CRC_LEN = 2;
+constexpr size_t LORA_ACK_DOWN_PAYLOAD_LEN = 7; // flags(1) + batch_id(2) + epoch_utc(4)
+static_assert(LORA_ACK_DOWN_PAYLOAD_LEN == 7, "ACK_DOWN payload must remain 7 bytes");
+
+constexpr size_t lora_frame_size(size_t payload_len) {
+  return LORA_FRAME_HEADER_LEN + payload_len + LORA_FRAME_CRC_LEN;
+}

 enum class LoraMsgKind : uint8_t {
  BatchUp = 0,